Question 1147426
<br>
5-12-13 and 8-15-17 are Pythagorean Triples.  So<br>
sin u = -5/13 in quadrant III  -->  cos u = -12/13
cos v = -15/17 in quadrant III --> sin v = -8/17<br>
Then<br>
{{{cos(u+v) = cos u * cos v - sin u * sin v}}}<br>
Use a calculator....